Oldenshaw and Dimmock have taken up the Home Secretary's offer of the legendary Peel Research Fellowship at All Saints College, Cambridge. Their brief is to investigate the changing causes and nature of crime and, ultimately, to advise the police, the legislature, and the government.

Oldenshaw and Dimmock turn their attention to the eternal menace of organised crime. Two worlds: one reflecting upon the others dark reflection...

Dimmock is not investigating crime as vigorously as Oldenshaw would wish. Indeed, it could even be said that at present no-one except the villain is gainfully employed...

The underworld holds its own court, trying a man for allegedly stealing money from the protection racket fees he collected. Oldenshaw does a little research on Spindoe, the self-appointed judge, while Dimmock is preoccupied with the theft of his ancient bicycle...

Oldenshaw and Dimmock consider Money. they decide there are three kinds. The first is carried and spent. The second is unearned, and grows in the dark. And the last is other people's - limitless, twinkling...

The Fellows' first experiment within the field of crime they are surveying succeeds - up to a point. After all, they were not to know that Alec Spindoe's rawest recruit should like driving cars more than stealing them!

The fellows plan their own crime to catch a gang of crooks: the theft of radioactive isotopes from a government research station. As expected, the underworld hears of the scheme, and the Kerrigan gang decide to swoop first. The trap is ready to be sprung...

Oldenshaw loses a book on a train - nothing important, but irritating. As a result a girl's life hangs in the balance and Oldenshaw is forced to re-examine his own motives for studying crime. Neither Dimmock nor Mrs. Hollinczech like the look of the new Oldenshaw...

Dimmock receives a letter demanding £2,000. What's more, Oldenshaw wrote it. And it's not the only one he's sent; Spindoe has received a demand for £20,000, with threats to his wife if it isn't paid. Dimmock is appalled by the tactic, and Spindoe starts planning a big job...

Safebreaker George Bird is of little use to his friends behind the bars of Strangeways Prison, so underworld boss Kerrigan plans to spring him. The Fellows, still not on speaking terms, take a look at prison escape organisations.

The field full of folk that the Home Office asked the Fellows to scrutinise becomes for them - as it has always been for others - a battlefield. And many of those involved have been maimed for life.

Having resolved their difficulties, Oldenshaw and Dimmock consider for a moment the policeman. He is an interesting phenomenon...after all, very few animals select others of their kind to look after them.

For Heaven's sake, do not applaud the honesty of the Fellows. It is not even worth considering why they have not committed a crime. They live as if they had. In this episode, two men fight to defend their property...